Elevator control



Feb. 17, 1925. I 1,526,314

E. M. BOUTON ET AL ELEVATOR CONTROL 7 Filed Dec. 51, 1921 a wnggssss: Ed wvgmys d gar au on. l M ganlrfiLew/ls [ATTORNEY Patented Feb. 17, 1925.

UNITED STATES,

PATENT erries.

EDGABJII. BOUTON, OF -EAST PITTSBURGH, AND FRAN; E. LEWIS, OF-

PENNSYLVANIA, ASSIGNORS T WESTINGHOUSE ELECTRIC AND 'IANUFACTUB- ING COMPANY, A CORPORATION OF PENNSYLVANIA. I

ELEVATOR CONTROL.

Application filed December 31, 1921. Serial No. 528,387.

To all whom it may concern:

Be it known that we, EDGAR M. BOU'ION,

a citizen of the United States, and a resident of East Pittsburgh, in the county of Allegheny and .State of Pennsylvania, and

FRANK E. LEWIS, a citizen of the United States, and a resident ofEdgewood, in the county of Allegheny and State of Pennsyl- Vania, have invented a new and useful Improvement in Elevator Controls, of which the following is a specification.

Our invention relates to motor-control systems and-. it has particular relation to such systems of control as are employed in connection'with elevators, hoists and similar machines.

.An object of our invention, is to provide an automatic system of speed control which shall be simple in construction, and that shall-ensure smooth and economical operation of the driven'apparatus.

Another object of our invention is to provide means for guarding against overtravel, which might cause damage to the apparatus or injury to elevator passengers.

Other objects of our invention will be apparent from the following description and the appended. claims.

Broadly, the control of a shunt motor by means of armature series and shunt resistance isold, as well ,as control by means of shunt field resistance. However, many of the systems employed are'very complicated and require delicate adjustment and are easily deranged. Apparatus utilizing air or oil dash pots are satisfactory while proper adjustment is maintained. Automatic current limit and counter-electromotive force systems of speed-control and dynamic braking have been used with considerable success but still leave room for improvement.

We propose to employ a current-limit, counter-electromotive force or any other desired system for gradually shunting the :starting or armature series resistor, and, in addition to this system, we propose to convtrol the effective value of the armature shunt resistor and the efiective value of the shuntfield resistor by switches having a predetermined time element controlled by magnetic means.

Figs. 3, 4, 5 and 6 represent, diagrammaticall the successive steps employed in the acce eration of the motor.

Referring particularly to Fig. 1, a. shunt motor, having an armature 1 and a shunt field-magnet winding 2, is connected to a source of energy through conductors 3 and 4. The motor may be operatively connected, for example, to an elevator car and maintained at rest in its inoperative position b means of an electromagnetic brake 5. switch 6 is actuated mechanicallyby the electromagnetic brake for controlling a circuit comprising resistor 7 to regulate the braking action, as will be hereinafter described.

The direction of rotation of the motoris controlled by reversing switches 8, 9, 10 and 11. Dynamic-braking switches 12 and ,13 are mechanically connected to.the re cuit for the coil of the electromagnetic brake 5. Limit switches 16 and 17 are provided, one for each direction of travel, and complete the circuit in shunt to the coil of the electroma etic brake.

A starting'resistor 18 and an inductance coil 19, which are connected in series with the motor armature 1, are controlled by electromagnetic switches 21 and 22. A sectional resistor 23, which is in parallel relation with the motor armature and the inductance coil, is controlled by electromagnetic switches 24 and 25 that are normally' closed by means of springs 26 and 27. Electromagnetic switch 25 is provided with a damper winding, such as that shown and described in connection with Fig: 2. Adynamic-braking resistor 28 is connected in i parallel .to the armature 1 and the inductance coil 19, by switches 12 and 13, and is alsov in parallel relation to the resistor 23. An electromagnetic switch 29 controls a portion of resistor 23 and is controlled by the reversing switches so as to close its contacts after switches 12 and 13 are closed, thereby providing increased dynamic braking effect. A damper-winding is also providedior this switch.

A- sectional resistor 30 is connected in series with the shunt field-magnet winding 2. Field relays 31, 32 and 33 are arranged to control the efiective value of the field resistor 30. Relays 31 and 33 are provided with damper windings similar to that of switch 25, as shown in Fig. 2. Relay 31 is controlled, in a well known manner, by the,

last orhigh-speed point of a master switch (not shown). Relay 32 is initially controlled, in starting, by current from the source'of supply and, during dynamic braking, is maintained in its operative position by the counter-electromotive force of the motor armature 1. Relay 33 is controlled in accordance with the position of relay 32 and is also provided with a magnet having a copper damper winding.

t will be apparent that shunt field control is accomplished in two steps, as has been found necessary in the operation of the average motor.

Referring to Fig. 1 2 of the drawing, a coil of magnet wire is wound on a copper tube or damper winding 34 and the whole is mounted on an iron core 35. lVhen the coil is energized, a moving contact member or switch is attracted into engagement with a core 35, as is well understood by any one familiar with electromagnetic switches.

Upon closure of reversing switches 8 and 10 and line switch 14, a circuit is established for the motor armature 1 extending from line conductor 3 through line switch 14,. switch 8, armature 1, inductance coil 19, resistor 18 and switch 10 to line conductor 4. A. shunt circuit is also established from line switch 8 through switch 24, a section of resistor 23 and switch 25 to resistor 18.

A section of resistor 23 is,'therefore, in shunt relation to the motor armature l and the inductance coil 19. Operating coil of relay 32 is connected through the contact members The operating coil of the-electromagnetic brake 5 1s energized from a circuit extending from line conductor 3 through hne switch 14, reversing switch 8, switch 12,- a portion of dynamic-braking resistor 28, conductor 36 and operating coil of electromagnetic brake 5 to line conductor 4. The oper-:

ating coil of switch '29 is connected in parallel relation to the brake coil so that switch 29 is opened immediately upon the-closure of reversing switch 8 and line switchl4.

The release of thebrake permits the motor to start and accelerate to its lowest operating speed, corresponding to the firstp'oint of the conventional -master switch (not shown). The second operating speed is at-.

tained by opening switch '25 to insert additional armature shunt resistance. The

next higher operating speed is attained by 1 a portion of the shunt field resistor 30 in. v

. series with the field winding 2. The opening of relay 32 also efiects thebpening of relay 33, but the operation of relay 33 is delayed on accound of its inherent time element, which is induced" by the short-circuited damper winding 34 (see Fig. 2). It is well understood that the counter-electomotive force of self inductionis maintained for a considerable period of time by' the use of a winding of the character described. Therefore, after a period of time determined by the peculiar construction of relay 33, the relay armature is released and theenti're resister 30 is inserted in series with the field winding 2, whereby the maximum motor speed is attained.

Figs. 3, 4, 5and 6 represent, respectively, the circuits of the foregoing system of control as arranged when the controller is at its first, second, third and fourth operating speed points, respectively.

In slowing down and stopping the motor,

the motor connections are established substantially in the reverse order with respect tothe connections during acceleration by the successive closure of relays 31', 32 and 33. Next, resistor 18 and inductance coil 19 are connected in series with the armature 1, and the entire resistor 23 is reconnected in shunt relation to the motor armature 1 and the inductance coil 19. When the coil of switch 25 is deenergized, the switch closes after a period which is predetermined by the inherent time-element of the switch magnet. This period of time is suflicient to prevent reducing the effective value of the resistor 23 until the speed of the motor armature has been reduced to a. proper value. Speed reduction is accomplished smoothly at a maximum rate consistent with good commutation of the armature.

In the off position, dynamic braking is established by the opening of contactors 8 and 10, which causes the armature current to flow in'a local circuitcomprising a portion of resistor 23 and the inductance coil 19. With switches 8 and 10 in their fully open position, switch 13 is closed and a parallel dynamic-braking circuit is established comprising the armature 1, resistors 28 and 18 and the inductance coil 19. The opening of switch 8 de-energizes the operating coil of switch 29 which closes to reduce the effective value of resistor 23. The closure of switch 29 is delayed by its damperwinding, whereby a graduated dynamicbraking action is insured. Line switch 14 is opened simultaneously with the' opening of switches 8 and 10 and back-contact switch 15 establishes a local circuit comprising the coil of electromagnetic brake 5, resistor 7 limit switches 17 and 16 and back-contact switch 15. The opening of switch 14 dis- .connects the brake coil from line conductor 3, and the local circuit for the brake coil prevents too abrupt setting of the brake.

The operating coil of back-contact switch 15 is connected in shunt with the coil of the brake 5, when switch 15 is closed, and operating coil of switch 15 is energized by thecounter-electromotive force of the brake coil. A firm contact is thus insured between the contact members of switch 15. Switch 6, which is actuated by the brake, is adapted to close and short-circuit resistor 7 before thebrake is fully set.

It is evident that, by selecting resistor 7 of proper value, the time of setting of the brake .is predetermined to apply full pressure of the brake after the motor speed has been substantially reduced by dynamic brak ing. In case of over-travel, resulting from any unforeseen cause, limit switch 16- or limit switch 17 is opened, depending on the direction of rotation of the motor thus interrupting the local brake circuit and insuring application of maximum brake-shoe ressure in a minimum period of time. ynamic braking and mechanical braking are, in such an emergency, accomplished substantially simultaneously and the motor is stopped in the shortest possible time;

It should be noted that, when the master switch is returned quickly to its ofi' position, dynamic-braking connections are immediately established, but, in addition to the gradual insertion of armature shunt resistance, dynamic braking is commenced value.

with a'weak field, and the field is, thereafter, gradually strengthened to its maximum To' insure a sufficient time interval in which to build up the field, in addition to the time constant of the field itself, relay 31 is of a construction similar to that of switch 25 and is provided with a damper winding.

The reversing switches 9 and 11 operate to reverse the connections of the motor armature 1, and switch 12 is opened to interrupt the dynamic-braking circuit through resistor 28. The coil of electromagnetic brake 5 is energized through switch 13 instead of through switch 12, while the several switches for controlling the motor speed function as previously described for the opposite direction of rotation.

We have described a system,'in which the particular advantages lie in the provisions for graduated dynamic braking, wherein we have eliminated apparatus requiring considerable attention for maintenance, and.

which should, therefore, have wide application in motor control, particularly in passenger-elevator service. Continuity of service, with a minimum of personal attention from the engineer in charge, is recognized as of utmost importance in the design of elevator control systems. \Ve have found by experience that a constant period of time for graduated dynamic braking isthe most satisfactory, scheme for average load conditions. Also, the use of inductance in the armature circuit aids in graduating the dynamic-braking effect in proportion to variation in load, so that the motor is brought to rest as quickly as is consistent with safe and economical operation.

We claim as our invention:

1. The combination with a shunt motor and controlling means therefor, of an electro-magnetic brake having a shunt operating coil, a source of energy and a coil energized by the counter electromotive force of the brake coil for rendering said controlling means ineffective.

2. The combination with .a shunt motor and a line switch, of an electro-magnetic brake, a source of energy and a coil energized b the counter electromotive force of the br. e coil for-rendering the line switch ineiiective.

3. The combination with a motor'having a shunt field-magnet winding, and a resistor for connection in circuit with the winding, of a relay controlled by the counter electromotive force of the motor for controlling the resistor to effect an increase in the motor speed, and an electromagnetic damper winding for controlling the relay.

1. The combination with a motor having a shunt field-magnet winding and a resistor for connection in circuit with the winding,

of a relay controlled by the counter electromotive force of the motor for. controlling the resistor to control the motor speed and an ,electro-magnetic damper winding for controlling the relay.

5. The combination with. a shunt motor and two resistors for respective connection in series with, and in shunt relation to, the motor armature, of an electromagnetic switch for controlling one of said resistors to Vary the motor speed, and means for magnetically retarding the operation of V the switch for a predetermined length of time after the operating coil of the switchhas become .de-energized.

6. The combination with a shunt motor and two resistors for respective connection in series with, and. in shunt-relation to, the motor armature, of an electromagnetic switch which normally shunts a portion of the shunt resistor and which, when operated, renders the shunted portion of said resistor effective, and means for magnetically retarding the operation of the switch for a predetermined length of time after the operating coil has become de-energized.

7. The combination with a shuntfmotor and two resistors for respective connection in series with, and in shunt relation to, the motor armature, of a spring-closed switch which normally shunts a. portion of the shunt. resistor, an operating coil for opening the switch, and a short-circuit-ing dampercoil for magnetically delaying the closure of said switch for a predetermined length of time after the operating coil has become deenergiz'ed.

8. The combination with an electric motor and controlling means therefor, of an electromagnetic brake, a source of energy, a shunt circuit for the operating coil of the brake, for maintaining the counter-electromotive force of self-induction of said coil for a predetermined length of time after-the source of supply is interrupted, and a switch .for opening said short circuit.

' ,9. The combination with an electric motor and controlling means therefor, of an elecoperating coil, means for connecting said coil to said source of energy and for disconnecting the shunt resistor,-a-nd a switch actuated by said brake for shunting said resistor after said source of energy is interrupted and after said resistor is reconnected in circuit.

' 11. The combination with an electric motor and controlling means therefor, of an electromagnetic brake, a source of energy, a resistor for connection in shunt relation to the brake-operating. coil, means for connecting said coil to said source of energy and for disconnecting the shunt resistor, a switch actuated by said brake for shunting said resistor after said source of supply is interrupted and after said resistor is recon nected in circuit,and a limit switch for controlling said shunt circuits.

12. The combination with a motor having a shunt field-magnet winding and a source of energ of dynamic-braking means for the motor, and additional dynamic-braking means effective a predetermined time after the motor is disconnected from the source of energy.

In testimony whereof, we have hereunto subscribed our names this 23rd day of December, 1921.

EDGAR M. BOUTON. FRANK E. LEWIS. 

